The present invention relates to coverings for architectural openings, and more specifically to horizontal blinds, such as Venetian blinds designed to emulate the look of window shutters.
Venetian Blinds
Typically, a Venetian blind has a fixed top head rail which both supports the blind and hides the mechanisms used to raise and lower or open and close the blind. The raising and lowering is done by a lift cord attached to the bottom rail (or bottom slat). Thus, when raising a blind, at first only the bottom rail is being raised and the amount of force required is small. As the bottom rail is raised further, more of the slats are stacked on top of the bottom rail and thus progressively more force is required to continue to raise the blind. The largest amount of force will be required at the very top when literally the entire blind is being raised. In contrast, when the blind is fully lowered, only the bottom rail is supported by the lift cord. The rest of the weight of the blind is supported by the ladder tape which has tilt cables running to, and supported by, the head rail.
The slats that are supported from the head rail may be allowed to tilt so as to open the blind to allow a maximum of light through the blind, or to close the blind with the room side down (the edge of the slats which is closest to the room is facing down, which means that the other edge of the slats, the edge which is closest to the window or the wall, will be facing up), or close the blind with the room side up. In some of the prior art, such as U.S. Pat. No. 2,116,356 Laborda, U.S. Pat. No. 2,218,508 Gentile, U.S. Pat. No. 2,244,094 Wread, U.S. Pat. No. 1,952,739 Weisfeld, and U.S. Pat. No. 2,105,082 Johnson, the head rail of the blind does pivot in order to tilt the blind. However, in these designs, the head rail does not hide the mechanisms used to raise and lower or open and close the blind. Also, as will be discussed later, in these references in which the head rail pivots, it pivots along a fixed axis, typically along the centroid of the head rail.
In order to accommodate the raising and lowering of the blind, lift cords are generally present in a Venetian blind, hanging off of one end of the head rail. In order to facilitate the raising of the blind stack, the lift cords generally have at least a 1-1 ratio of travel of the lift cord to travel of the blind stack. A higher ratio may be used (such as a 2-1 ratio) so that the lift cord travels twice as far as the blind stack so that the effort required to raise the blind stack is approximately one half the effort that would be required if the ratio were 1-1. Ratios lower than 1-1 are not generally used, because the effort required to raise the stack becomes too large to be comfortable and convenient for the user. Tilt cables or tilt wands may also be present to accommodate the tilting open or tilting closed of the blind stack.
Shutters
Shutters typically have louvers (which are the equivalent of the slats in a blind), but these louvers cannot be raised or lowered. They can only be tilted open or closed. In many instances, the shutter frame may be hinged so that the entire shutter may be swung open or closed. There are no cables or cords hanging off a shutter. The tilting of the louvers is typically accomplished by a tilt bar which is pivotally connected to every louver. Each of the louvers tilts along a fixed axis, typically along the centroid of the louver. In shutters, the louvers are mounted on a frame. The horizontal pieces of the frame are called rails, and the vertical pieces of the frame are called stiles. The stiles attach to the rails to enclose the louvers. There is a clearance requirement between the shutter and the window in order for the louvers to have room to tilt open. This clearance is not noticeable, even when the shutter is tilted closed, because the stiles are always framing the louvers.